1. Field of the Invention
The present invention relates to an actuator and a material for electrodes of the actuator, more precisely relates to an actuator capable of greatly deforming a sheet member made of a polymer material by applying an electric field and a material for electrodes of the actuator.
2. Description of the Related Art
An actuator having a flexible sheet member made of a polymer material and a pair of electrodes respectively provided on both faces of said sheet member has been known. The sheet member is deformed by applying an electric field.
For example, a conventional actuator is disclosed in Japanese Patent Gazette No. 2000-49397. The actuator is shown in FIG. 17. The actuator 10 has a one-layer polyurethane film 12 and a pair of electrodes 11 respectively provided on both faces of the polyurethane film 12. Deformation (bending electrostriction) is occurred by applying an electric field to the actuator 10. The electrodes 11 are formed on the both faces of the polyurethane film 12 by evaporating gold.
When the electrodes 11 are formed by evaporating gold, fine particles of gold are stuck onto surfaces of the polyurethane film 12.
By applying the electric field to the actuator 10, the actuator 10 bends as shown in FIG. 18. Therefore, the actuator 10 can be used to actuate other members. By employing the bending action, various kinds of actuators can be realized.
However, the deformation is so small, e.g., curvature 1/R=36 m−1 (see the Japanese patent gazette), that usage of the actuator must be much limited.
The inventors of the present invention studied and found that the deformation of the actuator was limited by a structure of the electrodes 11.
Namely, the electrodes 11 are formed by evaporating gold, so the fine particles of gold are stuck on the polyurethane film 12 by evaporation and keep contact each other. When the actuator 10 having such electrodes 11 is deformed, the electrodes 11 are cracked so that electric conduction is stopped. Therefore, the actuator 10 cannot be greatly deformed itself. If the electrodes 11 are made thick so as not to be cracked, the polyurethane film 12 cannot bend.